Anyone remember the days when we had a young struggling team with boneheaded point guards and Tommy would constantly scream... "RUN!!!!!... RUNNNNN!!!!!!!!!"
The two key components necessary for a fast break team (according to Tommy) was to have a rebounding big man who knew how to instantly kick the ball out... and a fast point guard with great instincts to push tempo.
I think Perk and Rondo fit those two roles pretty nicely. I think Rondo might be one of the best "fast break" point guards in the game, but I'm not sure we really have a "fast break" team around him. If you replaced Ray with a younger athletic guy like Iggy, you would lose a little in the half court set (less shooting spreading the floor)... but if you get a finisher who can run with Rondo, it would definitely give this team a different dynamic going forward. Something to think about.
Not to mention Iggy is pretty much better than Ray in every way other than shooting. If we actually could pull off a trade like that, we'd be insane not to do it.